<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
        #d1 {
            width: 100px;
            height: 100px;
            border: 1px solid red;
            /*margin-left: 50px;*/
            /*margin: 50px; 同时为4个方向赋值*/
            /*margin: 50px 100px; 上下和左右赋值*/
            margin: 10px 20px 30px 40px; /*上右下左顺时针赋值*/
        }
        #d2 {
            width: 100px;
            height: 100px;
            border: 1px solid blue;
            margin-top: 20px; /*上下外边距取最大值*/
        }
        #s1 {
            border: 1px solid blue;
            margin-right: 50px;
            /*margin-top: 100px; 行内元素无法设置上下外边距*/
        }
        #s2 {
            border: 1px solid blue;
            margin-left: 20px;/*左右相邻外边距相加*/
        }
        #big {
            width: 200px;
            height: 200px;
            background-color: red;
            overflow: hidden;/*解决粘连问题*/
        }
        #big>div {
            width: 50px;
            height: 50px;
            background-color: green;
            margin-left: 50px;
            /*当元素的上边缘与上级元素的上边缘重叠时,
            给元素设置上外边框会出现粘连问题*/
            margin-top: 50px;
        }
        body {
            margin: 0; /*去掉自身外边距*/
        }
        h1 {
            margin: 0; /*去掉自身外边距*/
        }
        *{
            margin: 0; /*去掉自身外边距*/
        }
    </style>
</head>
<body>
    <h1>这是h1</h1>
    <div id="big">
        <div></div>
    </div>

    <span id="s1">span1</span><span id="s2">span2</span>
    <div id="d1"></div>
    <div id="d2"></div>
</body>
</html>